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Phoghat writes "In what is starting to become a familiar theme, researchers have speculated on what types of observational data from distant planetary systems might indicate the presence of an alien civilization. Potential indicators of the presence of an alien civilization might include: atmospheric pollutants, like chlorofluorocarbons – which, unlike methane or molecular oxygen, are clearly manufactured rather than just biogenically produced; propulsion signatures – like how the Vulcans detected humanity in Star Trek: First Contact; evidence of stellar engineering – where a star's lifetime is artificially extended to maintain the habitable zone of its planetary system; or debris created from asteroid mining."

Potential indicators of the presence of an alien civilization might include: atmospheric pollutants, like chlorofluorocarbons â" which, unlike methane or molecular oxygen, are clearly manufactured rather than just biogenically produced

Dyson spheres (or swarms) would probably be the best way to detect an advanced civilization, especially a Kardashev Type II or Type III civilization.

In a Dyson sphere (or swarm) a civilization surrounds an entire star to capture most or all of its luminosity; severely cutting down on its optical luminosity but accentuating the IR luminosity. (The physics of a rigid sphere surrounding a star are pretty challenging, and some sort of swarm or cloud seems more likely, at least to our limited technological understanding.) So, to hunt for a Dyson sphere, you look for objects with an unusual excess of IR, and a lack of optical light. The IRAS IR satellite was used to search for Dyson spheres within ~ 1000 light years of the Earth [arxiv.org] (producing a handful of so-so candidates). Carrigan [arxiv.org] calls these sorts of searches "Interstellar Archaeology." They have one great advantage in that they don't require any cooperation from the other end (i.e., no beacons or other signals).

As it happens, I have recently speculated that "Object X [arxiv.org]" in M33 (the Triangulum Galaxy) could represent the signature of a Dyson sphere / swarm from 3 million light years away [americafree.tv]. If this (unlikely) possibility were to be true, it would represent the signature of a Kardashev Type III or near Type III civilization. Interstellar Archaeology is the only possible form of SETI across such vast distances.

The linked PDF you provided speculates that "object X" might be a self-obscured star, obscured by its own ejecta.

If we assume that this is indeed a dyson swarm, then the purpose might not be exclusively for collecting energy.

A category II or III civilization would be doing asto-architecture, and would need tremendous amounts of raw materials. Heavy atoms are only produced naturally in one kind of environment: in the hearts of stars. If this star is regularly expelling large quantities of cosmic dust, as the linked article postulates, then it would make an excellent "Factory". Energy would be in copious abundance, and the star itself would be churning out millions of tons of heavy atoms every minute. Even with a short (compared to other stars) lifespan, it would make an excellent factory site for other large astro-engineering projects.

It would be far more economical than mechanically processing already aggregated matter clumps (planets, asteroids, etc)-- especially with a dyson sphere/swarm infrastructure. The emitted gas and dust would be strongly ionized, and a simple network of magnetic traps could passively funnel the more desirable metal and halide ions from the lighter non-metals, with very minimal post processing. It would go a long way toward eliminating material scarcity issues that would otherwise plague a category II or III civilization.

Spectrographic analysis of the dust cloud to see if it has an uneven distribution of heavy and light elements would be quite revealing if this is the case-- Heavy ions would be in greater concentrations nearer the solar mass than away from it-- contrary to what you would expect if it was merely a gravitationally bound stellar dust cloud. (the latter would have a fairly uniform distribution of dust and gas)

Sadly, since it is in another galaxy such spectrographic studies are not very easy to do in sufficient resolutions to make such distinctions. It would need to transit some other more luminous celestial object in order for us to get such a reading, so that the invisible gas envelope surrounding the object could be studied, but again, it being in a distant galaxy coupled with the slow rate of orbital rotation of stars around a galactic center mass makes this a wait that could be billions of years long for such an event.